Truly portable, one-hand held-detectors of biological substances have not been commercially available. What has been available has been clinical kits that detect specific organisms. However, there is not presently any system that is capable of detecting organisms, protein toxins and biological substances in general, particularly if the system is to be used outdoors under less than totally tranquil circumstances.
It has been recently found to be possible to detect live, viable microorganisms by way of an inherent enzyme or enzymes. In this system live bacteria could be interrogated by their inherent enzymes that can be probed by certain compounds. Unfortunately for this system, only three enzymes can be probed; namely esterase, beta-galactosidase and glucosidase. The probe is limited because only three suitable compounds are commercially available and these are orthonitrophenylacetate, herein known as ONP acetate, ONP galactoside and ONP glucoside.
A number of techniques exist for the detection of bacteria in general. These techniques include the use of an excitation-emission matrix, 3-laser flowthrough cytometry, glucuronidase enzymes, aminopeptidase enzymes, extracellular enzymes and extracellular enzymes with nutrients. All of these techniques evoke a fluorescence response and require from 15 minutes to about four hours to achieve that response. Similarly, other techniques provide some of the sought after answers over a range of from 15 minutes, such as polarized light scattering to produce a Mueller matrix, to 9 hours where hydrogen and carbon dioxide are evolved over about 9 hours. Yet other techniques include gas chromatography to provide an ethanol metabolite, radiometry to produce CO.sub.2, electrochemical techniques generating a hydrogen metabolite, simple organism growth to produce electrical impedance, and a light-addressable potentiometric sensor to provide a redox potential response. Also, enzyme linked lectinosorbent assay provides a lectin-conjugate, and extracellular enzymes provide a colorimetric response.
None of these techniques is effective over very short periods of time, measured in seconds from as low as one second up to a maximum of 90 seconds or thereabouts.
Another drawback for the above enumerated techniques is the inability to detect small or micro-small quantities of the desired bacteria and the like, in the order of 200 or 300 bacteria in a given period of time.
Also, most of the above described techniques are difficult or impossible to use in the field and under outdoor conditions that do not permit tranquil operation of the device. Devices that depend upon complicated equipment do not survive in the field while comparative methods such as colorimetric methods and spectrophotometric measurements are not practical or even useful in some environments.
Accordingly it is an object of this invention to provide a method for detecting bacteria in general in a relatively short period of time of no more than about 90 seconds.
Another object of the present invention is to provide a system that can detect low levels of bacteria in short periods of time.
Yet another object of the present invention is to provide a method for detecting bacteria using a technique that employs vapor pressure rather than colorimetric or spectrophotometric measurements.
Other Objects will appear hereinafter.